Structural Integrity of 3d Printed Hardtop
 

Has anybody experimented with using 3d printed components for aerodynamic parts? I have seen several wings made from printed segments reinforced with threaded rods or fiberglass and canards, spats, other small components.

Lately I have seen a few people on the internet selling cad files for printable hardtops that are printed in segments and joined by various methods (plastic welding, rivets, glue, dowels, etc.)

I have no delusions that such a component would provide any support or improved safety in the event of a rollover; that's what the roll bar and door bars are for; but I have seen numerous people run aftermarket "race grade" fiberglass hardtops on track that are presumably significantly lighter (thinner) than an OEM fiberglass top.

It has been demonstrated that a hardtop provides a substantial reduction in lift and drag at speed; I know that a printed top would do exactly the same, but am unsure how substantial the aerodynamic loads at play are; a hardtop has a LOT of surface area so even a miniscule differential pressure could result in large loads at the mounting points.

I have a track car, and I have a printer, but I do not have a hardtop. $200 worth of filament and some glue is a tempting proposition for a substantial aerodynamic improvement but in my mind the safety on track is nebulous at best.

I think most people use these print files as a mold to make a final product in fiberglass/carbon. I've not seen anyone use ONLY filament. Would it work? I have no idea.

You can directly skin these in fiberglass and they would be more than stong enough.

I agree with Wingman, the best approach is to use it as a form for a material that has strength in many directions, like fiberglass or carbon fiber.

Even the best filaments don’t do well when the stress is carried through layer-to-layer adhesion. The distance from the windshield header to the area supported by the body (above your roll bar) is quite long and unsupported. I think you’d have to take print direction into account while planning that area.

I also question whether you can get enough high-strength filament for $200/hardtop. It’s a really, really big item to print, even if it’s thin.

Then there’s the cost of the special glue to adhere the sub-assemblies. I don’t think you can or want to go with fasteners for this. Specialist glue won’t be cheap.

And finally, I honestly don’t know if it would pass tech. We don’t have anything specifically prohibiting it, but it might fall into the category of “poses a danger to driver and/or other cars”. If it fails at speed, it’s going to be an underwear changing event for you and anyone behind you.

Seems excessive, just print in some PA6-CarbonFiber filament and save some steps.

I've been printing parts in PPA-CF and holy shit is the support difficult to remove DAYUMMMM

To be honest, I have (almost) zero actual 3D printing experience. But I’ve watched a lot of videos of people who are using it for cool things. For the most part, they seem to acknowledge, but gloss over, weakness due to layer adhesion.

In injection molded fiber-reinforced plastics, the fibers are (probably) oriented in all kinds of directions, providing some really nice strength against bending.

In cloth-based layups, (CF or glass), the layers are carefully oriented so that they are at angles to each other, so that the fibers are again, going in all kinds of directions, providing strength.

In filament based 3D prints, it would seem to me that the fibers would be oriented mostly in line with the filament. And I don’t think that they’d be crossing between layers much, if at all. Maybe they’d connect two print layers at most.

On a big, thin sheet like a hard top, I think you’d have an easy time snapping the print along a layer line.

Am I wrong about this? Please educate me.

Caution: I know nothing about this stuff.

My starting point would be to use the print as template/mould. Put a layer of CF top and bottom, maybe with some strategically placed holes/slots to bridge the two high strength surfaces.

But if you are going to do something like that, might as well just use it as a mould and make a multilayer CF structure. Cheaper, lighter and certainly strong enough. Lightyear's CF top that I ran for a while was configured as bolt-on, and impressively light and rigid - way to go for a race top.

I've been printing stuff in PETG-CF to make molds to make things out of CF. :rofl:

Seriously, who has a FDM printer big enough for this nonsense and who has the time for it?

https://cimg1.ibsrv.net/gimg/www.mia...4f19ab9a3b.jpg

I was honestly just making a joke. Mostly about how we already have "Carbon Fiber" like filament. It is what we like using in FossCAD, or 3dPrinted Guns. No idea if it would actually hold up to being used. If someone wants to buy the files and some rolls of filament for me, I will gladly print one out and attempt to assemble it.